Temperature sensing element



June 10, 1958 A. L. GOOD 2,837,918

TEMPERATURE SENSING ELEMENT Filed March 9, 1956 'f FIG. I 23 INVENTOR.

ARTHUR l GOOD ATTORNEY United States Patent TEMPERATURE SENSING ELEMENTArthur L. Good, Elkhart, Ind., assignor to Penn Controls Incorporated,Goshen, Ind, a corporation of Indiana Application March 9, 1956, SerialNo. 570,4sa

1 Claim. c1. 73--368.4)

This invention relates generally to temperature sensing elements andparticularly to a dual thermal sensing element capable of responding toa temperature change, the response being accommodated in independentenergy transmission systems.

In the control of domestic hot water heating systems, for example, it isoften required that the circulator operating control and the hightemperature limit control each have a water temperature sensing bulblocated in the Water circulating system at approximately the same spot.In the past dual temperature sensing bulbs have been accommodated in asingle bulb sheath or well. If the bulbs and well are circular incross-section, a form giving maximum rigidity and strength, then withthe two cylindrical bulbs inserted side by side in the cylindrical well,a substantial volume of air space must exist between the inner surfaceof the well wall and the bulbs; the heat transfer from the well walls tothe bulbs is, therefore, relatively slow. If the bulbs are shaped, otherthan circular in cross-section, so that all of the inner surface of thewell wall is in contact with one or the other of the bulbs, therebyincreasing the rapidity of heat transfer, then the departure from thecircular cross-sectional shape must be .payed for by a loss in strengthand rigidity of the bulbs.

A principal object of the present invention is to provide a dual bulbassembly in which the bulbs are formed of a cross-sectional shape givingmaximum strength and yet having a relatively rapid heat transfercharacteristic with respect to its enclosing sheath or well.

A further object is to provide a dual bulb assembly in which the bulbsare substantially concentric and coextensive, the inner bulb beingsupported at both of its ends.

A further object is to provide a dual bulb assembly wherein the bulbvolumes can more readily be controlled, the assembly being so formed asto lend itself to mass production machines and techniques.

These and other objects will be made apparent by the detaileddescription hereafter set out and the drawing in which:

Figure 1 is a sectional view of the dual bulb assembly and its enclosingsheath or well.

Figure 2 is an end view of one of the elements shown in Figure 1.

Reference numeral refers to a panel member which may be secured by anysuitable means to a control member or switch assembly (not shown).Member 10 carries rigidly mounted thereon, a bushing member 11. A sheathor well support element 12 is rigidly mounted on the member 11 by meansof setscrew 13 and a cooperating groove in the member 11. A tubular wellmember 16 having an outer closed end is secured by any suitable means,such as solder to the outer end of the element 12. Element 12 isexternally threaded and is thereby adapted to be inserted into a fluidcontainer or conduit.

Slidably mounted within the well member 16 is an elongated tubular bulbmember 17, having an outer closed end bottomed against the closed end ofmember 16. The inner open end of the bulb member 17 is closed by aflanged header member 18, which is sealed, by any suitable means, intothe bulb member 17. An inner bulb member 19 is nested within the bulbmember 1'7 and is supported at its closed end by contact with the end ofmember 17. The opposite end of member 19 extends through and is sealedto a central opening 21 in the header 18. A radially offset opening 22provides a path for fluid communication between the space defined by thewalls of bulb members 17 and 19 and a conventional capillary tube 20.The tube 20 provides a fluid transmission conduit to a power element 23,of a conventional type, which may be mounted with the control assembly(not shown). Similarly, a capillary type tube 24 independently connectsthe inner bulb member 19 to a power element 26 similar to the powerelement 23.

In operation, the well member 16 is-adapted to extend into a fluid thetemperature of which is to be sensed. Heat from the fluid is conductedthrough member 16, through the walls of bulb member 17 to the thermallyresponsive fluid filling the space between bulbs 17 and 19. The matchingcircular cross-section configuration of well 16 and member 17 provide amaximum area of heat conducting contact. The thermally responsive fluidfilling the space between the bulb members 17 and 19, consequently,reflects the temperature of the fluid surrounding the well member 16with a relatively small time lag.

The thermally responsive fluid filling bulb 19 receives heat, in turn,by conduction through the liquid between bulbs 17 and 19 and through thewalls of bulb l9. Depending on the relative size, in cross-section, oftubes 17 and 19 and therefore on the volume of fluid between members 17and 19, the response of the fluid within bulb member 19 will be somewhatslower than the response of its companion system. The inner bulb member19 may be formed of somewhat thinner less rigid stock than the outerbulb member 17 since it need Withstand only the pressure differencebetween the two independent thermally responsive systems,

From the foregoing it will be apparent that the present inventionprovides a dual bulb assembly which because of the tube and headerconstruction lends itself to mass production. In addition, the relativevolumes of bulb members 17 and 19 can readily be controlled. Theconstruction wherein the outer bulb 17 is closely nested within wellmember 16 and bulb member 19 is supported at both its ends provide arigid and strong assembly. Alterations may be made in the disclosureherein presented without departing from the scope of the invention whichis to be limited only by the appended claim.

What is claimed is:

A dual thermal responsive bulb assembly adapted to independentlyaccommodate the thermally sensitive fluid for a dual fluid pressuretransmitting system comprising an elongated tubular outer bulb havingone closed and one open end, an inner bulb generally concentric withsaid outer bulb and coextensive therewith, one end of said inner bulbbeing in supporting engagement with the closed end of said outer bulb, aheader member closing the open end of said outer bulb and supporting theadjacent end of said inner bulb, means including openings in said headermember providing independent fluid passages to both said outer and innerbulbs, and a well assembly adapted to support and sheath said bulbassembly.

References Cited in the file of this patent UNITED STATES PATENTS2,135,078 Hubbard et al. Nov. 1, 1938 2 477,835 Smith Apr. 12, 1949FOREIGN PATENTS 228,687 Switzerland Sept. 16, 1943

